Bimetal Thermometer with PT100 RTD Sensor Temperature Transmitter

Bimetal Thermometer with PT100 RTD Sensor Temperature Transmitter

Summarize 

Bimetallic thermometers are made up of bimetallic strips formed by joining two different metals having different thermal expansion coefficients. Basically, bimetallic strip is a mechanical element which can sense temperature and transform it into a mechanical displacement. This mechanical action from the bimetallic strip can be used to activate a switching mechanism for getting electronic output. Also it can be attached to the pointer of a measuring instrument or a position indicator. Various techniques such as riveting, bolting, fastening can be used to bond two layers of diverse metals in a bimetallic strip. However the most commonly used method is welding. Since two metals are employed to construct a bimetallic strip, hence they are named so.

Bimetallic thermometer is used for field testing of low or middle temperature ( from -80°C to 500°C), Can directly measure the temperature of all kinds of liquid, steam and gas medium.

 Feature 

 1.Local Display , robust and inexpensive.

2.Accuracy is between +or- 2% to 5% of the scale.

3. Stand 50% over range in temperaures.

4.All-Stainless Construction

5.Hermetically sealed 

6.Standard NPT connections 

7.OEM Logos Dials/Custom Dial

8.Dials sizes DN60,DN80,DN100,DN120,DN150

  Measurement range and applicable range

  Ambient condition

  Principle 

The bimetallic thermometer consists of a bimetallic strip. A bimetallic strip is made of two thin strips of metals which have different coeffcients of expansion. The two metal strips are joined together by brazing, welding or reveting so that the relative motion between them is arrested.

The bimetallic strip is in the form of a cantilever beam. An increase in temperature will result in the deflection of the free end of the strip as shown i diagram. This deflection is linear and can be related to temperature changes.

The radius of the curvature of the bimetallic strip which was initially flat is determined using the following relationship.

R= t{3(1+m)² + (1+mn)[m²+1/mn]}/6(ah-al)(T2-T1)(1+m) ²

where,
R= radius of the curvature at the temperature T2.
T = total thickness of the bimetallic strip = (t1+t2)
m=t1/t2 = Thickness of lower – expansion metal/thickness of higher – expansion metal.
l= coefficient of expansion of lower expansion metal.
h= coefficient of expansion of higher expansion metal.
T1 = Initial temperature.
T2 = temperature.